The exercise category of steppers includes both upright and recumbent devices designed for both exercise and rehabilitation of certain conditions. Recumbent steppers are a relatively recent addition to the category, originally designed to provide a full body work-out for those recovering from cardiac episodes. Aside from providing cardiovascular exercise, the major advantage of recumbent steppers is their ability to accommodate a joint range of motion (from extension to flexion) of less than 110°, a figure that devices based on circular pedal require.
U.S. Pat. No. 5,356,356 issued Oct. 18, 1994 to Hildebrandt et al. discloses a recumbent exercising device that works both the upper and lower extremities and includes an integrated, adjustable seat. In the Hildebrandt device, the action of the arm levers are coupled together and the action of the foot pedals are coupled together and the upper and lower halves are contralaterally synchronized to simulate a natural “walking” motion. Resistance is generated magnetically, providing constant, smooth, and adjustable effort.
While the action of the lever arms (both upper and lower) and contralateral synchronization provides a familiar and natural motion, the dependence of the lever arms restricts range of motion in the elbow joint and knee joint, respectively, if the range of motion is not identical side-to-side. In other words, each joint is not allowed to work to its respective abilities because the joint with the least range of motion dictates how long the stroke length will be because the motion is dependent.
U.S. Pat. No. 6,790,162 issued September 2004 to Ellis et al. discloses a similar recumbent exercising device, working both the upper and lower extremities and also including an integrated, adjustable seat, but the two foot pedals and two arm levers employ a one-way clutch so that the action of each respective movement is independent and not coupled together as found in the U.S. Pat. No. 5,356,356. In addition in the Ellis device the upper half and lower half are not synchronized in any way. A stop structure is employed to limit movement in both fore/aft directions and resistance is provided by way of eddy current brake. However magnetically (or eddy current) generated resistance is speed dependent, so the resisting force is only constant at a constant operator rate. This device allows each joint to work to its respective abilities due to the use of a one-way clutch and resulting independent movement, but the resisting force is common to both sides. This has the effect of the weakest leg and/or arm dictating the amount of resistance and not allowing the stronger arm and/or leg to work to its muscular ability.
In this single resistance generator arrangement, the resisting force works against all operator inputs. Therefore if more than one limb is moving against the resistance at the same time, the resistance felt by each limb will be less than if fewer (down to one) limbs are moving. This results in a varying resistance felt by the limbs as input movements overlap.
All of these devices transform the linear movement of the operator, into a circular motion about a fixed shaft, by means of a rigid mechanical connection to the shaft. This means the point of operator input, be it a foot pad or handle, travels in an arc centered on the fixed shaft. The result is that the input force of the operator is divided into a radial component and tangential component, relative to this shaft. Only the tangential component of the input force acting through the length of the input lever, creates torque to overcome the resisting torque and cause movement of the shaft and hence lever. Therefore, the current art requires a varying input force to move any input lever against a resisting force. The operator may not notice this variation, but for rehabilitation purposes, this is not a desirable condition and can cause injury to the recovering limb.
Accordingly it would be advantageous to provide a recumbent stepper that has a generally constant resistance force. It would be advantageous to provide a recumbent stepper wherein each pedal is operated independently such that the stroke length may be different for each leg and the resistance may be different for each leg. Further it would be advantageous to provide a recumbent stepper that can easily be used with different chairs including wheel chairs.